Bearing alloys of tin based white metal

ABSTRACT

THE TIN BASED WHITE METAL BEARING ALLOY IS IMPROVED BY ADDING 0.1 TO 1.5% OF CADMIUM, 0.001 TO 0.1% OF BERYLLIUM AND 0.005 TO 0.2% OF CHROMIUM TO THE TIN BASED WHITE METAL INCLUDING 78 TO 92% OF TIN, 5.0 TO 13% OF ANTIMONY AND 3.0 TO 9.0% OF COPPER.

1971 NOBUKAZU MORISAKI 3,563,732

BEARING ALLOYS OF TIN BASED WHITE METAL Filed July 24, 1968 2 Sheets-Sheet a FIG. 4 F 6 Kg/mm Kg/mm l6 I5 I m gm 5 Lu E /2 hg/o a R 6 IS United States Patent Oifice 3,563,732 Patented Feb. 16, 1971 3,563,732 BEARING ALLOYS OF TIN BASED WHITE METAL Nobukazu Morisalki, Nagoya, Japan, assignor to Daido Metal Company Ltd., Nagoya, Japan, a corporation of Japan Filed July 24, 1968, Ser. No. 747,368 Claims priority, application Japan, Feb. 9, 1968, 43/ 7,755 Int. Cl. C22c 13/00 US. Cl. 75-175 1 Claim ABSTRACT OF THE DISCLOSURE The tin based white metal bearing alloy is improved by adding 0.1 to 1.5% of cadmium, 0.001 to 0.1% of beryllium and 0.005 to 0.2% of chromium to the tin based white metal including 78 to 92% of tin, 5.0 to 13% of antimony and 3.0 to 9.0% of copper.

The present invention relates to bearing alloys, particularly to bearing alloys of white metal.

Alloys containing tin as a base metal and antimony and copper added thereto are generally used for bearing alloys. The bearing alloy of tin based white metal is bonded with backing material of steel as a lining, and applied to bearings, which is considered suitable for highspeed and heavy load bearing alloy. Said alloy has such a structure as Cu Sn of the acicular crystal structure (9 phase) and SbSn of the square crystal structure (,8 phase) are distributed in a soft matrix metal, and such soft matrix metal is excellent in its surface characteristic as bearing and the compatibility with the surface of a rotary shaft, and further, the hard compounds above mentioned distributed are also excellent in the wear resistance and load capacity, a combination of which produces favorable features of the bearing alloy.

However, this white metal alloy does not always satisfy the high toughness, the high temperature strength, the fatigue resistance. Marine diesel engines have been manufactured in larger sizes in recent years, so that high toughness, intensive high temperature strength, and high fatigue resistance are required. The present invention is to provide such bearing alloy of tin based white metal as to satisfy these requirements.

Generally bearing alloys of tin based white metal have such composition as 78-92% tin (Sn), 5l3% antimony (Sb), 39% copper (Cu), and 04% lead (Pb).

Among them, alloy containing tin of about 83% or more, but no lead, is employed to high speed and heavy load bearing alloy. This alloy is, however, apt to crack due to the repeated frictional force in case of heavy load. In this alloy the fatigue limit is low because of its relatively low impact resistance. It has been, therefore, impossible to use such alloy for bearings of large marine diesel engines, which are subjected to large repeated loads, especially large impact load. It is well known that in hearing alloys the generation of crack is related to the tensile strength, the impact load resistance is related to the toughness, and spread of crack is mainly related to the fineness of the structure. It is, therefore, possible to prevent development of crack by means of increasing the tensile strength of the alloy, to increase the resistance against the impact load by means of increasing the toughness, and also to increase the resistance against development of crack by means of making fine the structure, that is, making small the grain size of the crystals in e and 5 phases.

The quenching treatment from the high temperature is a well-known technique to make fine the structure of bearing alloy of the tin based white metal. However, this alloy is usually molten and welded to a backing material of steel to fix it thereto and also to reinforce its strength as a bearing, and therefore, in case of using the thick wall backing material of steel, the rapid cooling is difficult, so that it is impossible to make fine the structure. This matter is more conspicuous in large size bearings used for large marine diesel engines. In order to make fine these 5 and {3 phases, it has been attempted to add other elements, and consequently it has been found that the addition of such elements as cadmium (Cd), beryllium (Be), chromium (Cr), tellurium (Te), cobalt (C0), and the like, was effective.

According to the present invention, small quantities of of cadmium, beryllium, and chromium are added to the bearing alloy of the tin based white metal, whereby the tensile strength, the toughness, and the fatigue resistance of alloy are improved. A main object of the present invention is to provide such alloy.

An object of the present invention is to provide alloys having the tensile strength increased to reduce cracks being caused by the repeated frictioning in use, the toughness (elongation) increased to provide the high resistance against the impact load and the high fatigue resistance due to the fine crystal structure, as the result of addition of cadmium, beryllium and chromium to the tin based white metal.

According to the present invention, 0.1-1.5 cadmium, 0.0010.1% beryllium and 0.0050.2% chromium are added to the tin based white metal, on this occasion, usual alloy of tin based white metal is used, which consists of 7892% tin, 5-13% antimony, and 39% copper.

In accompanying drawings:

'FIG. 1 is a diagram which shows the relationship between the quantity of additive cadmium and the tensile strength of alloy in case of cadmium being added to a usual bearing alloy of tin based white metal;

FIG. 2 is a diagram which shows the relationship be tween the quantity of additive cadmium and the elongation of said alloy;

FIG. 3 is a diagram which shows the relationship be tween the quantity of additive beryllium and the elongation of alloy in case of beryllium being added to the alloy;

FIG. 4 is a similar diagram which shows the relationship between the quantity of additive beryllium and the tensile strength of the alloy;

FIG. 5 is a diagram which shows the relationship between the various quantities of additive beryllium and the variations in the elongation of bearing alloy of the tin based white metal of the present invention to the quantity of additive chromium;

FIG. 6 is a similar diagram which shows the relationship between the quantity of additive chromium and the tensile strength of the alloy;

FIG. 7 is a photomicrograph of 100 magnifications which shows the composition of a usual bearing alloy of tin based white metal; and

FIG. 8 is a photomicrograph of 100 magnifications which shows the composition of bearing metal of tin based white metal according to the present invention.

According to the present invention cadmium of 0.1- 0.5% is added to the usual alloy aforesaid, thereby the tensile strength of alloy is considerably increased. As shown in FIG. 1, the addition of 1.5% Cd increases the tensile strength up to about 11 kg./mm. However, the addition of 1% or more Cd considerably decreases the elongation (FIG. 2), and the hardness is raised up to about 40 of Hv.

FIG. 1 shows that in case of Cd added to alloy containing 4% Cu, 9% Sb and 87% Sn, as the quantity of additive Cd is increased, the tensile strength is raised. FIG. 2 shows the variation in the elongation in case of Cd added to the similar alloy, and as obviously shown in it, so far as the elongation is concerned, the addition of Cd beyond 1% or more considerably lowers the elongation, so that it is preferable not to add Cd of more than 1.5%.

Beryllium of 0.001-0.1% is added to said alloy according to the present invention. By that the tensile strength is not so considerably increased, but raised to a certain extent, however, the elongation is considerably increased. As shown in FIG. 5, alloy containing 0.04% Be shows about 17% elongation, while an alloy without the Be content represents about 10% elongation. And further, according to the additive quantity of Be, the 6 phase (Cu Sn and the ,8 phase (SbSn) are made fine.

FIG. 3 shows the variation of the elongation in case of Be added to the alloy, and, as obviously from FIG. 3, in proportion to the quantity of Be to be added, the elongation is increased. Be has very high dissolution loss, however, the increase in the elongation is recognized by the addition of 0.001% Be, and the addition of more than 0.1% of Be makes the structure coarse, which, therefore, produces a reverse effect.

In the present invention, chromium of 0.005 %-0.2% is added to the alloy, thereby there is no substantial increase in the tensile strength, but the elongation is increased, and also the 6 phase is considerably made fine.

According to the present invention, it is possible to produce excellent bearing alloy of white metal by the composite effects of Cd, Be and Cr. Such effects are as follows:

FIG. 5 represents the variation in the elongation according to the addition of Cr, in which the influence of Cr on the elongation is shown by two examples of 0.05% Be and 0.02% Be respectively added to alloys consisting of 3.8% Cu, 8.7% Sb, 1.0% Cd and 86.5% Sn. The curve A on FIG. 5 represents the relationship between the quantity of Cr to be added and the elongation in case of 002% Be added to said alloy, and the curve B represents the similar relationship in case of 0.05 Be added to said alloy. As mentioned above, and as obviously shown in FIG. 2, the addition of 1.0% Cd results in a decrease of the elongation. FIG. 5 is a diagram which shows the effect of Cr for the basic alloy added with 1.0% Cd. That is, in case of no additive Cr, the elongation is about 7.5%. Cu-S'b-Sn alloy without the Cd content has the elongation of about 10%. This shows that the former has an elongation lower than the elongation of the latter, and however, by means of adding Cr., the elongation is increased as shown in FIG. 5. The addition of Cd is necessary to increase the tensile strength, and it is an indispensable element with the object of the present invention. The decrease in the elongation due to the addition of said Cd is supplemented by the addition of Cr, and moreover the addition of Cr increases the elongation of tin-based alloy containing copper and antimony. Referring to FIG. 5, 3.8% Cu, 8.7% Sb, 1.0% Cd, 86.5% Sn alloy added with 0.02% Be, but without the Cr content, has about 7.5% elongation, however, according to the increase in the quantity of Cr, the elongation is increased, which is recovered up to 14% by the addition of 0.1% Cr, as shown by the curve A. Still further, as shown by the curve B, in case of said tin-base alloy with the 1% Cd and 0.05% Be contents, the elongation is considerably increased with the increase in Cr, and by means of adding 0.1% Cr, it exceeds 17%. Obviously this corresponds to the elongation in case of Be alone added to said alloy. This matter means that, notwithstanding the addition of Cd which significantly interferes an elongation, such interfering effect is removed by coexistence of Cr.

And further, FIG. 6 represents the condition of the tensile strength in case of Cr added to said 3.8% Cu, 8.7% Sb, 1% Cd, 0.02-0.05% Be alloy, as one of the composite actions of Cd, Be and Cr. As obviously shown in it, the tensile strength of this alloy without the Cr content is about 11 kg./mm. This tensile strength is not lower than the tensile strength in case of the 1% Cd and 0.1% Be being added, but rather shows a slight increase and further shows that this effect of increasing the tensile strength in Cd is not prevented by the increase in the Cr content.

The addition of Cd has such effect as to increase a tensile strength, but in case of the quantity exceeding 1%, it considerably lowers the elongation, so that the quantity has to be determined under the relative control to the tensile strength. In order to avoid the decrease in the elongation, it is preferable that Cd is added by the quantity of less than 1.5 and the increase in the tensile strength is recognized by the addition of 0.1% Cd, so that it is preferable to choose the quantity of Cd within the range of 0.1%-0.5%.

The addition of only 0.001%; Be increases the elongation, and the elongation increases in response to the increase in the quantity of Be, but no significant increase is produced beyond the range of 0.05%. However, the 6 phase and ,8 phase are made fine by the addition of Be, so that Be may be added up to 0.1% in the range in which the tensile strength is not substantially decreased.

The 6 phase is made significantly fine by the slight addition of Cr. However, there is no recognizable change in case of the addition of 0.2% or more, and beyond that range decreasing of the elongation and the tensile strength take place as an aging, so that the quantity of 0.2% will be the ceiling limit.

The addition of Cd produces the favorable tensile strength, but it unavoidably decreases the elongation. However, the addition of Be not only prevents the decrease in the elongation, but also increases the elongation, and moreover it makes fine the 6 phase and {3 phase simultaneously. As mentioned above, the 6 phase is made fine by Be, and the 5 phase is larger in quantity than the 13 phase, so that to make fine the 6 phase is important to improve the property of alloy, and such improvement is achieved by the addition of Cr.

It is, therefore, obvious that the addition of Cd increases the tensile strength and the hardness, the addition of Be makes fine the crystals of the 6 phase and the 5 phase, and the addition of Cr significantly makes fine the crystal of the 6 phase. The increase in the tensile strength obviously prevents alloy effectively from developing of crack caused by the repeated frictional actions while in use, the increase in the toughness and the elongation improves the impact resistance, and the fineness of the structure raises the fatigue limit of alloy, thereby alloy is suitably utilized to heavy load.

The comparison between the properties of bearing alloy of tin-based white metal according to the present invention and the conventional alloy is shown as follows:

Component, percent Properties Tensile Elonstrength gation Hardness Cu Sb Sn Others (kg/mm?) (percent) (11v) Conventional alloy 3. 71 7.06 Balance 7. 6 18.0 24. 5. 45 9. 53 do 8. 7 8.1 28. 2 3.16 7.15 do. Cd, Co, Cr 8.6 13. 4 28.0 3. 8.73 do Cd, Ni, Ag 10.0 14. 4 32.4

Alloy oi the present invention. 3.81 8.54 do Cd, Be, Cr 11.1 18.8 31.9

As obviously shown in the table above, the alloy of the The kinds of sample alloys are as follows:

Component, percent present invention is superior to the conventional alloys in tensile strength (kg./mn1. elongation (percent) and hardness (Hv).

Bearing alloy of tin based white metals are usually cast-welded to the surface of backing materials of steel, so that the Weldability is one of the essential properties in said alloys. In order to prevent the structure from becoming coarse, it is better to quench immediately after casting, however, such quenching treatment results in generating strain, peeling off from the backing material, and segregation, and further, it is impossible to obtain the good quenching effect in case of large size alloys. According to the present invention, the structure is made fine without quenching after casting, and even if the quenching treatment is used together, the structure is made fine further more. The addition of Be and Cr has such effect as to prevent peeling off from the backing material.

As mentioned above, according to the present invention, 0.11.5% Cd, 0.00l0.l% Be, and 0.0050.2% Cr are added to bearing alloy of tin based white metal containing 78-92% Sn, 543% Sb and 39% Cu, and thereby it is made possible to by the composite effects of these additives obtain bearing alloy having sufficient strengths against heavy load and impact load, and the fine structure.

The alloy according to the present invention is superior in its mechanical properties to the conventional alloys, and its fatigue resistance, which is one of the essential factors of the alloy, is also excellent. It was proved by the continuous test of revolution dynamic load as shown below. The result of the said test is as follows:

The sample hearings were produced respectively by welding and lining sample alloys to backing materials of steel by means of a centrifugal casting process, in which the inside diameter of bearing was 62 mm., the Width was 31 min, and the thickness of lining alloy was 0.3 mm. The number of revolution of a rotary shaft was 3,000 rpm, the peripheral speed was 9.7 m./sec., the bearing load was 250 kg./cm. the shaft was continuously rotated under the forced lubrication for the bearing, and the fatigue limit was determined to be such time as the region (area) of developing crack reached 10:5% of the total projected area of the bearing surface.

In the test as mentioned above, alloy No. l of the present invention had no recognizable crack after 50 hours. And alloy No. 2 of the present invention had also no recognizable development of crack after 59 hours. On the other hand, such crack as to correspond to the foregoing condition was recognized on conventional alloy No. 1 after 13 hours, which apparently indicated the fatigue limit. Similarly, conventional alloy No. 2 indicated the fatigue limit after 15 hours. Conventional alloy No. 3 having the 0.78% Cd content produced crack after 48 hours, prolonging its life by three times when compared with other alloys without containing Cd, which deems to be the influence of Cd. However, all the alloys of the present invention did not show the fatigue until 50 hours, which deems to be resulted from the addition of Be and Cr with Be.

As mentioned above, according to the present invention, the 6 phase and the [3 phase are made fine by the addition of Be, and the 6 phase is made fine by the simultaneous addition of Cr, and the microscopic observation of its structure is shown in FIG. 8. The similar structure of the conventional alloy without the Cd, Be and Cr contents is shown in FIG. 7. Both pictures are shown by 100 magnifications, in which it is obviously shown that the square crystal ([3 phase) is considerably small when compared with the conventional alloy shown by FIG. 7, and the acicular crystal (6 phase) is also considerably made fine.

What is claimed is:

1. An alloy consisting of, except for unavoidable impurities, by weight 39% of copper, 5-13% of antimony, 01-15% of cadmium, 0.00l0.l% of beryllium, 0.005 0.2% of chromium, with the remainder being tin.

References Cited FOREIGN PATENTS 1,021,975 3/1966 Great Britain -l75 714,504 12/1941 Germany 75175 HYLAND BIZOT, Primary Examiner E. L. WEISE, Assistant Examiner 

